1. Field of the Invention
The present invention generally relates to full-duplex transceiver circuits and associated methods.
2. Description of Related Art
Persons of ordinary skill in the art understand terms and basic concepts related to microelectronics that are used in this disclosure, such as “voltage,” “current,” “ground,” “resistor,” “capacitor,” “resistance,” “capacitance,” “signal,” “node,” “shunt,” “differential,” “single-ended” “common mode,” “DC (direct current),” “impedance,” “impedance matching,” “logical signal,” “transmission line,” “characteristic impedance,” “switch,” and “operational amplifier.” Terms and basic concepts like these are apparent to those of ordinary skill in the art and thus will not be explained in detail here.
If the logical signal is “high” (or “1”) it is said to be “asserted.” If the logical signal is “low,” (or “0”) it is said to be “de-asserted.”
A full-duplex transceiver is an apparatus configured to concurrently transmit a first signal using a transmitter and receive a second signal using a receiver. In practice, a part of the first signal often leaks into the receiver and combines with the second signal to form a third signal, which is what the receiver actually receives and has to process. The part of the first signal that leaks into the receiver is referred to as an “echo,” which is a noise that impairs the receiver and needs to be suppressed. In U.S. Pat. No. 8,045,702, Lin et at teach a hybrid circuit for use in a full-duplex transceiver to reduce the echo. The hybrid circuit, however, is based on differential signaling, wherein both the first signal transmitted by the transmitter and the second signal received by the receiver are differential signals. As widely known in the prior art, a differential signal comprises a first end, also known as a positive end, and a second end, also known as a negative end. In contrast, a single-ended signal comprises only a single end. While differential signaling offers numerous advantages, single-ended signaling is used in many applications thanks to lower complexity.
What are disclosed are method and apparatus of echo reduction for a full-duplex transceiver that utilizes single-ended signaling.